AGGREGATION-INDUCED EMMISSION

Aggregation can be regarded as a force of nature that drives similar entities to assemble and function as a broader dynamic organism. However, even until very recent times, a much broader opportunity of this phenomenon towards the developments of luminescent materials was hidden from our sight. It was generally considered (and observed) that the aggregation of luminescent dyes can only result in quenching of luminescence. In a breakthrough discovery in 2001, Tang et al. demonstrated that aggregation of flexible molecular systems can significantly improve their luminescence efficiency. This phenomenon of Aggregation-Induced Emission (AIE) is largely contributed to the restricted molecular motions of the luminescent units in their aggregated states. Following this report, a significant number of systems have been identified, developed, and applied as versatile AIE active materials finding applications in various aspects of material sciences e.g. biological evaluations, security, sensing, etc. [1] In recent years, we have been interested in the developments of AIE active based on NPIs. [2-3] NPIs are well known as p - synthons due to their strong intermolecular p-p interactions which also often lead to their emission quenching in aggregated or condensed-states. In our trials, systematic alterations of the NPI based molecular backbone in order to fine-tune their extended solid-state structures. It was found that a balance of intermolecular forces and molecular environment can be an effective recipe to impart AIE features in NPIs. Following these observations, we also noticed that incorporation of NPI with boron-containing dyes can result in broad emissive AIES (Aggregation-Induced Emission Switching) active materials. [4] Apart from these efforts, our group is also exploring the possibilities of D-A systems based on organometallic boron compounds.